Orbital Degeneracy–Driven Spin Regulation Enables Multi‐Electron Biomass Electrooxidation

ABSTRACT

The electrosynthesis of 2,5‐furandicarboxylic acid (FDCA), a renewable polymer monomer for degradable plastics, represents a promising strategy for biomass upgrading, yet remains fundamentally limited by the challenge of accommodating diverse reaction intermediates involved in the multi‐electron oxidation of 5‐hydroxymethylfurfural (HMF). Here, we demonstrate that facet‐controlled orbital‐degeneracy‐driven spin regulation in spinel NiCo ₂ O ₄ offers an effective strategy to accelerate the electrosynthesis of FDCA. The exposed (110) facet modifies the orbital splitting of active‐site Co and leads to a lifted Co 3d orbital degeneracy with a moderate‐spin‐associated electronic configuration. This electronic structure balances the adsorption‐desorption behavior of key intermediates and lowers the overall reaction barrier. Such a design enables complete HMF conversion with a 99.9% yield for FDCA, while an integrated NiCo ₂ O ₄ nanoarrays electrode with exposed (110) facets delivers Faradaic efficiencies of ∼94% under industrial‐level current densities, underscoring their scalability. These results establish a mechanistic framework for orbital–spin engineering in electrocatalyst design, offering broad implications for accelerating complex multi‐electron transfer reactions.